Quantitative Measurements

The fundamental role of any separation process is the isolation and quantitation of the individual components of a mixture. In the analysis of DNA by capillary electro-phoresis (CE), the migration time and the sample quantity are the basic parameters obtained from any electropherogram. Migration time is used to estimate the DNA fragment size, and the quantity of product gives the analyst polymerase chain reaction (PCR) reaction yields, the efficiency of an extraction process, or the level of expression of a particular gene. Chemical processes such as PCR amplification or restriction enzyme digestion can vary in their yield, making measurement of the product quantity a critical parameter. The need for exact quantitative measurements is increasing with the use of methods such as quantitative PCR, in which an analyte and an internal standard of similar sequence are amplified together and compared. Many different applications, such as mutational analysis, and the detection of length polymorphisms, require the ability to reliably detect the size of a DNA fragment. DNA typing can require the routine determinations of differences in fragment size of two bases or less.